Germany was defeated in World War I, and the Treaty of Versailles placed punitive conditions on the country, including significant financial reparations, the loss of territory (some only temporarily), war guilt, military weakening and limitation, and economic weakening. Germany was humiliated in front of the world and had to pay very large war reparations. Many Germans blamed their country's post-war economic collapse and hyperinflation on the treaty's conditions. These resentments contributed to the political instability which made it possible for Adolf Hitler and his National Socialist Party to come to power, with Hitler's appointment as Chancellor of Germany in 1933.

Full-scale war in Europe began at dawn on September 1, 1939, when Germany used her newly formed Blitzkrieg tactics and military strength to invade Poland, to which both the United Kingdom and France had pledged protection and independence guarantees. On September 3, 1939, the UK and France declared war on Germany and British troops were sent to France, however neither French nor British troops gave any significant assistance to the Poles during the entire invasion, and the German–French border, excepting the Saar Offensive, remained mostly calm.

On September 17, the Soviet forces joined the invasion of Poland, although remaining neutral with respect to Western powers. The Polish government evacuated the country for Romania. Poland fell within five weeks, with her last large operational units surrendering on October 5 after the Battle of Kock. As the Polish September Campaign ended, Hitler offered to Britain and France peace on the basis of recognition of German European continental dominance. On October 12, the United Kingdom formally refused.

Despite the quick campaign in the east, along the Franco-German frontier the war settled into a quiet period. This relatively non-confrontational and mostly non-fighting period between the major powers lasted until May 10, 1940, and was known as the Phoney War.

Several other countries, however, were drawn into the conflict at this time. By September 28, 1939, the three Baltic Republics felt they had no choice but to permit Soviet bases and troops on their territory. The Baltic Republics were occupied by the Soviet army in June 1940, and finally annexed to the Soviet Union in August 1940.

The Soviet Union wanted to annex Finland and offered a union agreement, but Finland rejected it, which caused the Soviet Union to attack Finland on November 30. This began the Winter War. After five months of hard fighting, Finns were only pushed from a strip of land bordering Russia, in spite of Soviet numerical superiority, the Soviet Union gave up attempts to subdue the whole country. In the Moscow Peace Treaty of March 12, 1940, Finland ceded 10% of her territory. The Finns were embittered over having lost more land in the peace than on the battlefields, and over the perceived lack of world sympathy.

On May 10 the Phoney War ended with a sweeping German invasion of Belgium, the Netherlands, Luxembourg, and French Third Republic that bypassed French fortifications along the Maginot Line. After overrunning The Netherlands, Belgium, and Luxembourg, Germany turned against France, entering the country through the Ardennes on May 13—the French had made the fatal mistake of leaving this area almost totally undefended, believing its terrain to be impassable for tanks and other vehicles. Most Allied forces were in Flanders, anticipating a re-run of the World War ISchlieffen Plan, and were cut off from the French mainland. As a result of this, and also the superior German communications and tactics, the Battle of France was shorter than virtually all pre-war Allied thought could have conceived. It lasted six weeks, including the Luftwaffe bombing of Paris June 3. On June 10 Italy declared war on both France and the United Kingdom, but did not gain any significant success in this campaign. French government fled Paris, and soon, France surrendered on June 22. In order to further the humiliation of the French people and the country itself, Hitler arranged for the surrender document to be signed in the Forest of Compiègne, in the same railway coach where the German surrender had been signed in 1918. The surrender divided France into two major parts; the Northern part under German control, and a southern part under French control, based at Vichy and referred to as Vichy France, a rump state friendly to Germany. Many French soldiers, as well as those of other occupied countries, escaped to Britain. The General de Gaulle proclaimed himself the legitimate leader of Free France and vowed to continue to fight. Following the unexpected swift victory, Hitler promoted 12 generals to the rank of field marshal during the 1940 Field Marshal Ceremony.

Later, on April 24, 1941, the U.S.S.R. gave full diplomatic recognition to the Vichy government situated in the non-occupied zone in France.[2]

Thus, the fall of France left Britain and its Empire to stand alone. The British Prime Minister, Neville Chamberlain, resigned during the battle and was replaced by Winston Churchill. Fortunately for Britain, much of its army escaped capture from the northern French port of Dunkirk, where hundreds (if not thousands) of tiny civilian boats were used to ferry troops from the beaches to the waiting warships. There is much debate over whether German Panzer divisions could have defeated these soldiers alone if they had pressed forward, since the tank divisions were overextended and would require extensive refitting; in any case, Hitler elected to follow the advice of the leader of German air forces Hermann Göring and allow the Luftwaffe alone to attack the Allied forces until German infantry was able to advance, giving the British a window for the evacuation. Later, many of the evacuated troops would form an important part and the center of the army that landed at Normandy on D-Day.

The British rejected several covert German attempts to negotiate a peace. Germany massed their air force in northern German-occupied France to prepare the way for a possible invasion, codenamed Operation Seelöwe (Sea Lion), deeming that air superiority was essential for the invasion. The operations of the Luftwaffe against the Royal Air Force became known as the Battle of Britain. Initially the Luftwaffe concentrated on destroying the R.A.F. on the ground and in the air. They later switched to bombing major and large industrial British cities in the Blitz, in an attempt to draw R.A.F. fighters out and defeat them completely. Neither approach was successful in reducing the R.A.F. to the point where air superiority could be obtained, and plans for an invasion were suspended by September 1940.

During the Blitz, all of Britain's major industrial, cathedral, and political cites were heavily bombed. London suffered particularly, being bombed each night for several months. Other targets included Birmingham and Coventry, and strategically important cities, such as the naval base at Plymouth and the port of Kingston upon Hull. With no land forces in direct conflict in Europe, the war in the air attracted worldwide attention even as sea units fought the Battle of the Atlantic and a number of British commando raids hit targets in occupied Europe. Churchill famously said of the R.A.F. personnel who fought in the battle: "Never in the field of human conflict was so much owed by so many to so few".

Pre-war doctrine had held that waves of bombers hitting enemy cities would cause mass panic and the rapid collapse of the enemy. As a result, the Royal Air Force had built up a large strategic bomber force. By way of contrast, Nazi German air force doctrine was almost totally dedicated to supporting the army. Therefore, German bombers were smaller than their British equivalents, and Germany never developed a fully successful four engined heavy bomber equivalent to the Lancaster or B-17, with only the similarly sized Heinkel He 177 placed into production and made operational for such duties with the Luftwaffe in the later war years.

The main concentration of German raids on British cities was from September 7, 1940 until May 10, 1941 in the most famous air battle of all time, known as the Battle of Britain. Facing odds of four against one the RAF held off the mighty Luftwaffe forcing Hermann Wilhelm Göring to withdraw his forces and more importantly indefinitely postpone invasion plans. This proved the first major turning point of the War. After that most of the strength of the Luftwaffe was diverted to the war against the Soviet Union leaving German cities vulnerable to British and later American air bombings. As a result of the victory, Great Britain was used by U.S and other Allied forces as a base from which to begin the D-Day landings in June 1944 and the liberation of Nazi-occupied Western Europe. Nevertheless, German raids continued on British cities albeit on a smaller and less destructive scale for the rest of the war, and later the V1 Flying Bomb and V-2 ballistic missile were both used against Britain. However, the balance of bomb tonnage being dropped shifted greatly in favour of the RAF as Bomber Command gained in strength. By 1942, Bomber Command could put 1,000 bombers over one German city.

From 1942 onwards, the efforts of Bomber Command were supplemented by the Eighth Air Force of the United States Army Air Forces, U.S. Army Air Forces units being deployed to England to join the assault on mainland Europe on July 4, 1942. Bomber Command raided by night and the US forces by day. On February 14, 1945, a raid on Dresden produced one of the most devastating fires in history. A firestorm was created in the city, and between 18,000 to 25,000 people were killed.[3][4][5] Only the raids on Hamburg (July 24, 1943 – July 29, 1943), the March 9–10, 1945 firebombing of Tokyo and the nuclear attacks on Hiroshima (August 6, 1945) and Nagasaki (August 9, 1945) killed more people through a single attack.

The Mediterranean and Middle East Theatre was a major theatre of operations during the Second World War. The vast size of this theatre included the fighting between the Allies and Axis forces in Italy, the Balkans, Southern Europe, Malta, North Africa and the Middle East.

Prior to the war Italy had invaded Albania and officially annexed it. Mussolini's regime declared war on Britain and France on June 10, 1940, and invaded Greece on October 28. However, Italian forces were unable to match the Nazi successes in northwest Europe. Italy declared war on Greece and invaded the country, but it was not until German intervention that the country was overrun. While the Greek campaign was underway, German forces, supported by the Italians, Hungarians and the Bulgarians simultaneously invaded Yugoslavia. After the mainland was conquered, Germany invaded Crete in what is known as the Battle of Crete. With the Balkans secure, Germany and her allies attacked the Soviet Union in the largest land operation in history. The Balkans campaign delayed the invasion[citation needed], and subsequent resistance movements in Albania, Yugoslavia and Greece tied up valuable Axis forces[citation needed]. This provided much needed and possibly decisive relief for the Soviets.

Fighting in Southern Europe would not resume until Axis forces were defeated in North Africa. Following the Axis defeat in Africa, Allied forces invaded Italy and during a prolonged campaign fought their way north through Italy. The invasion of Italy resulted in the nation switching sides to the Allies and the ousting of Mussolini. But, in spite of the coup, Fascists and occupying German forces retained possession of the northern half of Italy. In northern part of Italy, the occupying Germans installed Mussolini as the head of new fascist republican government, the Italian Social Republic or RSI to show that the Axis was still in force. But Mussolini and his Fascists were now puppet rulers under their German patrons.

By April 1945, German forces were retreating on all fronts in northern Italy and occupied Yugoslavia, following continuous Allied attacks. The campaign, and the fighting in the Mediterranean and Middle East Theatre came to an end on 29 April. On May 2, in Italy, Field Marshal Heinrich von Vietinghoff, the commander-in-chief of all German forces in the country surrendered to Field Marshal Harold Alexander, the supreme commander of all Allied forces in the Mediterranean area. Fighting would, however, continue in Greece where a civil war had broke out and end on 1949 after Greek government troops aided by the US and Britain defeated the communist guerrillas supported by the Soviets.

On June 22, 1941, Germany launched the invasion of the Soviet Union, code-named Operation Barbarossa.[6] This invasion, the biggest in recorded history, started the bloodiest conflict in world history; the Axis–Soviet War, also known as the Eastern Front. It is generally accepted as being the most lethal conflict in human history, with over 30 million dead as a result. It involved more land combat than all other World War II theatres combined.

The leader of the USSR, Joseph Stalin, had been warned repeatedly by outside sources and his own intelligence network of the impending invasion, but he ignored the warnings due to conflicting information presented to him by the Soviet intelligence[citation needed]. Moreover, on the very night of the invasion Soviet troops received a directive undersigned by MarshalTimoshenko and General of the ArmyGeorgi Zhukov that commanded: "do not answer to any provocations" and "do not undertake any actions without specific orders". The early weeks of the invasion were devastating for the Soviet Army. Enormous numbers of Soviet troops were encircled in pockets and fell into Nazi German hands. In addition to German troops, a few Italian, Hungarian and Romanian and Finnish troops were involved in the campaign. Finland initially declared neutrality, however with both German and Soviet troops on her soil, Finland was well prepared to join forces with Germany when the Soviet Union attacked on June 25. The following conflict from 1941 to 1944 is sometimes referred to as the Continuation War, as in the continuation of the Winter War.

Operation Barbarossa suffered from several fundamental flaws. The most serious of these was the logistical situation of the attack. The sheer vastness of the distances in the Soviet Union meant that Germany could only advance so far before outrunning their supply chains. By the time the German attack froze to a halt before Moscow on December 5, 1941, it literally could not go any further. There simply were not enough supplies reaching the front to conduct proper defensive operations, let alone a proper offense. The timetable that Barbarossa was planned to assume that the Soviets would collapse before the Russian winter hit. The failure of that to happen also fatally affected Nazi German plans. Had Hitler not invaded Greece and Yugoslavia earlier in the year, the invasion would have proceeded at that time[citation needed], and the Soviet Union might have collapsed.

During their long retreat, the Soviets employed a scorched earth policy. They burnt crops and destroyed utilities as they withdrew before Germany. That helped to contribute to the logistical problems that Germany experienced. More importantly for them, the Soviets also succeeded in a massive and unprecedented removal of their industry from the threatened war zone to protected areas in the East.

The extension of the campaign beyond the length that Germany expected meant that the German Army suffered hundreds of thousands of casualties in the bitter cold of the Russian winter, and from the counterattacks of Soviet units.

Even with their advance having ground to a halt due to a lack of supplies and the onset of winter, Germany had conquered a vast amount of territory, including two-fifths of the Soviet economy. Dislodging them proved difficult and eventually cost the Soviet Union dearly.

A few months after the invasion began, German troops came to southern approaches to Leningrad and laid a siege to the city (known as the Siege of Leningrad), which was also blocked from the north by Finnish forces. Finland's C-in-C Mannerheim had halted at the River Svir and refrained from attacking the city. Hitler had ordered that the city of Leningrad must "vanish from the surface of the earth", with its entire population exterminated. Rather than storming the city, the Wehrmacht was ordered to blockade Leningrad so as to starve the city to death, while attacking it with bombers and artillery. About one million civilians died in the Leningrad siege – 800,000 by starvation. The siege lasted for 872 days. The only overland way into the city was possibly during the winter, across the frozen Lake Ladoga, between the German and Finnish lines.

After enduring the winter of 1941–1942, the German army prepared for further offensive operations. One of the major problems faced by the Nazi war machine in World War II was a shortage of oil. For this reason,[citation needed] Germany decided to give up on Moscow for the time being, and the summer offensive of 1942 decided to focus on the war in the south, with the target being the oil fields of the Caucasus. Meanwhile, the Soviets had their own plans.

Beginning of the campaign turned into a strategic disaster for Soviets whose Southern flank was nearly destroyed. Surviving Soviet units were pushed hundreds kilometres to the east and the Wehrmacht advance went almost uncontested. But in a major blunder, Hitler split Army Group South into two subgroups, Army Group A which would attack the Caucasus and Army Group B which would advance towards the city of Stalingrad (now Volgograd).

Indecision by Hitler, dissent among the higher-ranked Nazi German officers, and extended supply lines combined in a prolonged battle in the streets of Stalingrad. Germany eventually occupied over 90% of the city, but in an attempt to defeat the remaining Soviet defenders almost all German soldiers in the area were funnelled into the ruins of the city. Months of bitter hand-to-hand combat in the ruins of the city depleted the German forces, leaving only weak Romanian and Hungarian forces to guard the flanks of the Stalingrad army group.[citation needed] In Operation Uranus, the Soviets easily defeated these minor Axis forces as they performed a massive encirclement operation. The German troops remaining in the city were trapped – cut off from their supply lines and starving, amidst a harsh winter, they were ordered by Hitler to fight to the last man, and they displayed[when?] incredible fortitude and bravery under unbearable conditions.

Starved of food, fuel, ammunition, and clothes, the pocket was gradually reduced, with the last portion surrendering on February 2, 1943. In a cynical attempt to prevent the surrender, Hitler promoted Friedrich Paulus, commander of the 6th Army to Field Marshal, because no German of that rank had surrendered before. Heavy losses affected both sides in the Battle of Stalingrad, one of the most costly battles in history. About 1.5 million people perished in this battle, including 100,000 civilians in the city.

After Stalingrad, the initiative had passed from Germany but had not yet been seized by the Soviets. A desperate counterattack in the spring of 1943 by forces of Field Marshal Erich von Manstein temporarily halted the Soviet advance. Battle of Kursk was the last major offensive by the German Army on the eastern front. The Soviets had intelligence of what was to come and prepared massive defences in huge depth in the Kursk salient. They stopped the German armoured thrusts after a maximum penetration of just over 30 miles (48 km). After Kursk the Red Army got the upper hand and generally was on the offensive for the rest of war, and the large scale of the Soviet Union allowed to overcome high losses in manpower and equipment. Soviet success prompted a more active Allied involvement on the opposite of Europe, because Nazi Germany was bogged into a costly defensive war on the East, fending its ever shrinking occupied territory.

Pushing the enemy out of the Soviet territory in 1944, Soviet Army proceeded to dismantle minor Axis powers, namely Romania, Slovakia, Bulgaria, and Hungary, to liberate this and other neighbouring countries from the Nazi yoke, and to impose communist-led governments on the liberated nations. Some of these nations joined Allies and provided troops to fight the Nazi Germany, effectively the only Axis remainder in Europe by the end of 1944. Finland retained its independence the second time, but broke with the Axis, at the cost of necessity to fight the former ally and some more territorial cessions to the USSR.

More Soviet citizens died during World War II than those of all other countries combined. Nazi ideology considered Slavs to be "subhuman" and German forces committed ethnically targeted mass murder. Civilians were rounded up and burned alive or shot in squads in many cities conquered by the Nazis. Approximately 27 million Soviets, among them more than 20 million civilians in Soviet cities and areas, were killed throughout the duration of the war.

At least 7 million Red Army troops died facing the Germans and their allies in the Eastern Front. The Axis forces themselves had lost over 6 million troops, whether by combat or by wounds, disease, starvation or exposure; another several hundred thousand[citation needed] were seized as POWs and a substantial part of them died in Soviet captivity because of disease or shortage of supplies.

Lend-Lease supplies from the United Kingdom and the United States made very important impact for Soviet military forces. Supply convoys sailed to Soviet ports that were patrolled by Nazi U-boats. Allied activities before D-Day may have tied up only a few divisions in actual fighting, but many more were forced to guard lonely coasts against raids that never came or to man anti-aircraft guns throughout Nazi-controlled Europe.

Simultaneously with the fall of Rome came the long-awaited invasion of France. Operation Overlord put over 180,000 troops ashore in Normandy on June 6, 1944, creating a beachhead that would eventually result in over 3 million Allied soldiers on Germany's western front. A long grinding campaign six weeks long followed as American, British, and Canadian forces were slowly built up in the beachhead, and German forces slowly worn down. When the breakout finally did come it was spectacular, with Allied troops very quickly capturing almost all of Normandy within days. Many German forces that had been fighting in Normandy were trapped in the Falaise pocket.

Incessant bombing of Germany's infrastructure and cities caused tremendous casualties and disruption. Internally, Hitler survived a number of Nazi inner assassination attempts. The most serious was the July 20 Plot, occurring on July 20, 1944. Orchestrated by Claus von Stauffenberg and involving among others Erwin Rommel and Alfred Delp, the plot had intended to place a time bomb in a position to kill Hitler but a number of unscheduled factors and operation failures led to its failure. Adolf Hitler was only slightly injured.

Operation Overlord was complemented by an invasion of southern France on August 15, 1944 codenamed Operation Dragoon. By September 1944 three Allied Army Groups were in line against German formations in the west. There was optimism that the war in Europe might be over by the end of 1944.

An attempt was made to force the situation with Operation Market Garden (September 17, 1944 – September 25, 1944). The Allies attempted to capture bridges with an airborne assault, to open the way into Germany and liberate the northern Netherlands. Since heavier German forces than intelligence had predicted were present, the British 1st Airborne Division was almost completely destroyed, and the operation failed.

The weather of 1944 combined with a poor situation for the Allies led to a stagnant situation on the western front. The Americans continued to grind away at the defenders in the Battle of Hurtgen Forest (September 19, 1944 – February 10, 1945). As long as Germany stayed on the defence, the Allies were hard-pressed to advance rapidly.

That changed when Germany mounted a major counteroffensive on December 16, 1944. The Ardennes offensive, also called the Battle of the Bulge, drove back and surrounded some small American units. The Allied forces were eventually successful in driving back Germany, in what turned out to be their last major advance of the war. The battle officially ended on January 27, 1945.

The final obstacle to the Allies was the Rhine. It was crossed in March 1945, and the way lay open to the center of Germany. The last major German forces in the west were encircled and trapped in the Ruhr.

On April 27, 1945, as Allied forces closed in on Milan, Mussolini was captured by Italian Partisans. He was trying to flee Italy to Switzerland and was traveling with a German anti-air battalion. On April 28, Mussolini and several of the other Fascists captured with him were taken to Dongo and executed by squad shooting. The bodies were then taken to Milan and unceremoniously strung up in front of a filling station.

Hitler, learning of Mussolini's death, realized that the end had finally come. He remained in Berlin, the crumbling Nazi capital, even as the city was encircled and trapped by the Soviets and the Battle of Berlin raged. On April 30, Adolf Hitler, with his wife of one day, Eva Braun, committed suicide in his bunker to avoid capture by Soviet troops. In his last will and testament, Hitler appointed Grand Admiral Karl Dönitz as the new German leader. But Germany lasted only 7 days longer under the "Flensburg government" of Dönitz. He surrendered unconditionally to the Americans, British, and Soviets on May 8, 1945.